No doubt, you will hear a lot about this comet in the coming year. Although the press is incorrectly using ISON as it’s name, the designation is only to identify the location of the discovery organization. The official ‘name’ is C/2012 S1. If it was named, it would be Comet Nevski-Novichonok, after its discoverers. But whatever you call it, this comet has the potential to be the brightest comet that anyone alive has ever seen. The operative word is POTENTIAL. Forecasting the brightness of comets is notoriously difficult. Remember the 1973 Comet Kohoutek or the more recent Comet Elenin?

C/2012 S1 (ISON) [C:9x300s]

Here is what astronomers know:

The comet will come very close to the sun. Perihelion on the 28th of November has the comet coming as close as 680,000 miles above the surface of the sun. Close to the sun means more energy to form a tail or it means enough energy to destroy the comet.

The comet will come fairly close to the Earth. Perigee on the 26th of December has the comet coming as close as 39,000,000 miles from the Earth.

The currently calculated orbit is parabolic implying this is an Oort cloud comet on it’s first pass through the solar system. If true, this means the comet may have a lot of volatile components to form a long, bright tail. It also means there is no way to predict if the comet is strong enough to survive the pass.

C/2012 S1 (ISON) [C: 9x300s]

These images were taken on the 3rd of January and I measured the brightness at a 16.7 magnitude. As usual, North is to the right and East is up. The comet shows a East to West motion.

At the time the comet was above the ecliptic, outside the orbit of Jupiter, and on the same side of the Sun as the Earth. It will not drop below the ecliptic until November when it is still inbound and between the orbits of Earth and Venus.